This invention relates to an engine control that breaks the torque lock typically found in a transmission with engaged gears, allowing the transmission to be moved to neutral without actuating the clutch.
Heavy vehicles, such as trucks have an engine driving the wheels of a vehicle through a multi-speed transmission. The transmission is moveable through several speed ratios at the control of a manual input switch.
A manual transmission typically slides a clutch collar relative to different gears to engage one of the gears. To complete a shift, the operator must first typically move the gear that is presently-engaged out of engagement to a "neutral" position. In some transmissions, the movement out of engagement is performed by a hydraulic piston. In the "neutral" position, the transmission does not engage any gear, and thus rotational drive is not transmitted to the transmission output shaft from the engine crank shaft.
This movement from an engaged position to a neutral position occurs while drive force from the engine is being transmitted. When the transmission is engaged and rotational drive is being transmitted from the engine to the transmission, there is a large torque load holding the gears and the clutch collar together at a particular axial position. This torque load makes it quite difficult for an operator, or the piston, to move the clutch collar out of engagement. This so-called "torque lock" typically makes it impossible to move a transmission to neutral without somehow reducing the torque load. To this end, vehicles with manual transmissions have historically been equipped with clutches. An operator actuates the clutch which breaks the coupling between the engine and the transmission. The torque load goes to zero, and the operator is able to move the gear out of engagement.
In the heavy vehicle industry, the operation historically necessary to complete a shift between gears is relatively complicated. Typically, a driver must actuate the clutch, and then begin modifying the engine speed through the accelerator to synchronize engine speed to a speed necessary for the next speed ratio to be engaged. At the same time, the operator must manually move the gear shift lever to engage the gear in the proper new gear. These procedures become more burdensome when a driver is rapidly shifting through several sequential gear changes.
Control devices have been developed which calculate the transmission output torque and the engine input torque and then adjust the engine input torque until it matches the transmission output torque. When the torques match, the torque load is zero and a shift may be made without clutching or manipulating the accelerator or brakes for a "clutchless" shift.
The calculations that the control device has typically processed to achieve this result have been rather complex, requiring the use of many inputs and processing space. Also the control devices sometimes cannot be integrated into the main engine controller, and as a result, the number of inputs available and the processor size is reduced. To this end, it is desirable to provide a more simplified calculation while maintaining or improving upon the accuracy produced by prior control devices.